1. Field of the Invention
The present invention relates to a CRT (cathode ray tube) socket and, more particularly to a construction that is effective in reducing the thickness of a CRT (Cathode Ray Tube) socket that connects a CRT to a color television set, a display monitor, or the like.
2. Description of the Related Art
CRTs are widely used in color television sets and display monitors. While there is a demand for CRTs with wider screens and higher resolutions, there is also a demand for reduction in the depth of such devices.
FIG. 4 is a perspective drawing showing a conventional CRT socket 101. FIG. 5 is a cross-sectional view of the terminal pins of a CRT and the connecting portion of a CRT socket.
The CRT socket 101 has a cylindrical central hole 105 passing through it from its front face to its rear face. The CRT socket 101 includes a ring-shaped portion 102 that is concentric with and surrounding the cylindrical central hole 105. A cover portion 103 is fitted over a base portion 104 with the rear face of the cover portion 103 corresponding to the rear face of the base portion 104. A pair of focus contacts 107, into which the high-voltage focusing terminal pins of a CRT are inserted to connect the pins, are located at positions on the cover portion 103 that are concentric with the central cylindrical hole 105. Signal contact holes 106, into which the low-voltage signal terminal pins are inserted to connect the pins, are also provided at positions on the ring-shaped portion 102 that are concentric with the central cylindrical hole 105.
A CRT, or xe2x80x9cBraun tubexe2x80x9d as it is sometimes called, is a glass tube whose inside is a near vacuum. As shown by the dot-dot-dash line in FIG. 5, a CRT has a neck portion 100 containing an electron gun. A stem base 100c is provided so that a vacuum sealing portion 100d covers the end of the neck portion 100. Focusing terminal pins 100a and signal terminal pins 100b for the electron gun are also provided. The focusing terminal pins 100a are connected to focus contacts 172 of the CRT socket. The signal terminal pins 100b are connected to signal contacts 162.
The voltage applied to the signal terminal pins is relatively low, with a magnitude of 0 to 1000V. On the other hand, a high voltage in a range of 5 kV to 10 kV is applied to the focusing terminal pins. In order to electrically insulate the surrounding parts from the focusing terminal pins, the focusing terminal pins are surrounded by an insulating resin wall 142.
As a result, when attempting to reduce the thickness of the CRT socket, sufficient insulation is required for the focusing terminal pins. Making the focusing terminal pins shorter can easily result in problems affecting the quality of the electric connection of the focusing terminal pins and can make it necessary to reassess the manufacturing method of a CRT. This problem has complicated the task of making further reductions in the thickness of a CRT socket.
According to the above, it is an object of the invention to provide a CRT socket that is thinner while avoiding the drawbacks of the prior art.
It is a further object of the invention to provide a CRT socket construction that enables the thickness of the CRT socket to be reduced while maintaining favorable insulation, without requiring a change in the neck of a CRT.
According to an embodiment of the invention, there is provided a slimline CRT socket, comprising: a ring-shaped portion that has a cylindrical central hole passing therethrough from a front face to a rear face thereof, a plurality of concave signal contact housings in the rear face of the ring-shaped portion at positions that are concentric with the cylindrical central hole, signal contacts in a different one of the signal contact housing, and signal contact holes on the front face of the ring-shaped portion to allow signal terminal pins of a CRT to be inserted into the corresponding signal contact housings so as to connect the signal terminal pins to the signal contacts; a cover portion; the cover portion includes a focus contact housing formed as a concave in a rear face thereof, a focus contact in the focus contact housing, and a focus contact hole that allows a focusing terminal pin of the CRT to be inserted so that the focusing terminal pin is connected to the focus contact; and a base portion corresponding to the rear face of the cover portion, wherein a concave focusing terminal pin housing that houses the focusing terminal pin is disposed on the base portion, the focusing terminal pin housing concave passing through a surface of a board that is attached to the CRT socket and projecting outward from an opposite surface thereof.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.